In polyorganosiloxane compositions forming rubbery elastic bodies by curing at room temperature, the composition of the type which undergoes a curing reaction by contact with the moisture in air does not involve complicated procedures such as weighing a base polymer, a crosslinking agent or a catalyst, or mixing them directly before use, and thus involves no problem in compounding, and is excellent in adhesive property. Therefore, such a polyorganosiloxane composition has been widely used as elastic adhesives or coating materials in the electric and electronic industries and also as a sealant, etc., for buildings.
Such a polyorganosiloxane composition is generally composed of a silanol group-terminated polydiorganosiloxane, wherein the terminals of the molecule are blocked with hydroxyl groups, compounded with a crosslinking agent having on the average more than 2 hydrolyzable groups in the molecule and according to the kind of the crosslinking agent used, the composition releases a carboxylic acid (e.g., acetic acid), an organic amine, an amide, an organic hydroxylamine, an oxime compound, an alcohol, an acetone, etc., upon curing.
In those compositions, the composition releasing acetic acid exhibits excellent in adhesive properties and curing properties, but in the case of using that composition, there are problems in that care must be taken as to the irritative odor generated can make the working environment unpleasant. Further, when an article to which the composition is applied is a metal, some way to prevent corrosion is necessary to prevent the metal from being rusted.
When a composition which releases a long chain carboxylic acid is used, there is no problem in generating irritating odors but it is difficult to prevent rusting of metals, in particular, rusting of metals after they are immersed in water.
Similarly, in the amine-releasing type composition, there is a problem in that the amine released has a strong odor and can be toxic, and in the hydroxylamine-releasing type, oxime-releasing type, and amide-releasing type compositions, there is a problem in that they are liable to rust metals, in particular copper and copper alloys. Furthermore, the acetone-releasing type composition is cured quickly and does not have a corrosive property, but there is a problem with such composition in that the synthesis of the crosslinking agent therefor is not easy and the uncured composition is severely yellowed during storage.
On the other hand, the alcohol-releasing type composition has the advantages that not only is an alkoxysilane, which is the crosslinking agent, available at a low cost but also, since the released material is an alcohol, such as methanol, ethanol. etc., while the released material is liable to volatilize off, there is still no problem with odor nor is there a problem with corrosion. On this other hand, the composition has the disadvantages that curing thereof is slow and the storage stability is poor since the alcohol generated by the hydrolysis of the crosslinking agent with a slight amount of water existing in the system during the storage thereof can harm the base polymer, and hence it has been desired to overcome disadvantages.
In particular, a room-temperature curable polyorganosiloxane composition is frequently used as a rubbery elastic body by curing while in contact with a copper series metal for use of an adhesive, coating material, etc., in the electric and electronic industries. Recently, the oxime-releasing type, acetone-releasing type, and alcohol-releasing type compositions have been used for the above-described purpose, but since those compositions have the earlier described disadvantages, it has been desired to develop a room-temperature curable polyorganosiloxane composition free from the disadvantages earlier described.
On the other hand, a one-part type room-temperature curable polyorganosiloxane composition composed of a polyorganosiloxane having alkoxy groups bonded to the terminal silicon atoms, an alkoxysilane, a curing catalyst, and an alcohol scavenger has recently been found and it is disclosed that this composition has good storage stability and has rapid curing capability; it also has been disclosed that a silicon-nitrogen bond containing compound is effective as the alcohol scavenger (PCT Japanese Patent Publication Nos. 59-500219 and 58-501040). Also, a room-temperature curable polyorganosiloxane composition using a silicon-nitrogen bond compound having a hydrolyzable group as the alcohol scavenger so that the compound can be utilized as a crosslinking agent after reacting with the alcohol is disclosed in JP-A-60-135458 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") and a room-temperature curable polyorganosiloxane composition which is improved to show less corrosive property to copper-series metal is disclosed in JP-A-60-123552.
Such room-temperature curable polyorganosiloxane compositions which have a rapid curing property and do not rust copper series metals are used as adhesives and coating materials in the electric and electronic industries. However, recently, in the electric and electronic industries, electric contact hindrance with volatile components (low molecular weight materials) is becoming a serious problem. That is, the volatile components contained in the adhesives and coating materials, such as a low molecular weight siloxane and a small amount of additives as described above (the alcohol scavenger, etc.) volatilize from the composition during curing and from the surface of the cured material after curing to sometimes cause electric contact hindrance. Hence, a countermeasure for the problem has been desired.